The present invention relates to a data communication apparatus and a method to mutually communicate data among a plurality of devices by using a directional signal as a carrier wave.
Data communication systems using an infrared ray are classified as follows.
Type 1: A transmission apparatus of directivity radiates an infrared ray of narrow beam width, and a receiving apparatus of narrow view angle directly receives the infrared ray.
Type 2: The transmission apparatus of directivity or a transmission apparatus of indirectivity radiates an infrared ray of wide beam width, and a receiving apparatus of wide view angle directly receives the infrared ray.
Type 3: The transmission apparatus of directivity radiates an infrared ray of narrow beam width, and a receiving apparatus of wide view angle directly receives the infrared ray.
Type 4: The transmission apparatus of directivity or the transmission apparatus of indirectivity radiates an infrared ray of wide beam width, and the receiving apparatus of narrow view angle directly receives the infrared ray.
Type 5: The transmission apparatus of directivity radiates an infrared ray of narrow beam width, and the receiving apparatus of narrow view angle receives the infrared ray reflected by the ceiling or the wall of the room.
Type 6: The transmission apparatus of directivity or the transmission apparatus of indirectivity radiates an infrared ray of wide beam width, and the receiving apparatus of wide view angle receives the infrared ray reflected by the ceiling or the wall of the room.
Type 7: The transmission apparatus of directivity radiates an infrared ray of narrow beam width, and the receiving apparatus of wide view angle receives the infrared ray reflected by the ceiling or the wall of the room.
Type 8: The transmission apparatus of directivity or the transmission apparatus of indirectivity radiates an infrared ray of wide beam width, and the receiving apparatus of narrow view angle receives the infrared ray reflected by the ceiling or the wall of the room.
The types 1, 2, 3, 4 are called line of sight (LOS) link type communication system because a receiving side directly receives the infrared ray radiated by a sending side. The types 5, 6, 7, 8 are called a non-line of sight (LOS) link type communication system because the receiving side does not directly receive the infrared ray radiated by the sending side. As a condition of the view type communication system, the transmission side and the receiving side exist in a view area line of sight. If an obstacle object exists between the transmission side and the receiving side, the communication is not executed. On the other hand, the non-view type communication system uses a diffusion light reflected by the ceiling or the wall. Therefore, even if the transmission side and the receiving side are not located in the view area, the communication is executed. Especially, the type 6 is called an infrared ray communication system of diffusion type, whose free degree of communicatable device location is largest among the above eight types.
However, in the infrared ray communication system, it is not always assured that a particular device (own terminal) can communicate to all other devices surroundingly existed. In short, a hidden terminal to which the direct light and the reflected light do not reach often exists. For example, naturally, the particular device can not communicate to other devices spaced more than the maximum communicatable distance away. It is possible that a neighboring device becomes the hidden terminal because the infrared ray is not transmitted by the obstacle object. Furthermore, in case a plurality of devices are located to mutually communicate, all devices must be located in a common area in which communicatable areas of the all devices overlap. If at least one device is not located in the common area, mutual communication is not executed.
FIGS. 1A and 1B show an example of mutual communicatable area for a plurality of devices. In FIGS. 1A and 1B, a communicatable area of the infrared ray communicatable device 91 is 910, a communicatable area of the infrared ray communicatable device 92 is 920, a communicatable area of the infrared ray communicatable device 93 is 930. In order for the devices 91, 92, 93 to mutually communicate, the communicatable areas of the devices 91, 92, 93 must overlap. As a result, a mutual communicatable area is limited. In addition to this, if another device 94 appears, the other device 94 must be located so that all communicatable areas of the devices are overlapped. If the device 94 is located as the communicatable area 940 shown in FIGS. 1A and 1B, mutual communication of four devices 91, 92, 93, 94 is impossible.
In FIGS. 1A and 1B, the communicatable area of each device is represented as a circle or a rectangle. However, actually, the communicatable area is transformed by direction of the sending apparatus and effect of the obstacle object. In proportion to increase of a number of devices, the mutual communicatable area is further limited.
As a method to extend the mutual communicatable area, an infrared ray repeater including a transmitter and a receiver for the infrared ray is used. This infrared ray repeater has a function to reflect a light signal and retransmit the received light signal after amplification. However, even if the infrared ray repeater is used, the infrared ray does not have a transparency of substance such as a wireless wave of ISM (Industrial Scientific Communication) band, and its ability of diffraction is low. Therefore, it is difficult that the infrared ray repeater is located at communicatable position for all devices in comparison with a repeater of a wireless wave. At a place where the infrared ray repeater is not located at communicatable position for all devices, it is difficult that the mutual communicatable area is extended by using the infrared ray repeater.
Furthermore, in case N devices set communication paths of connection type to mutually communicate, N(Nxe2x88x921)/2 connections must be set and each device must manage (Nxe2x88x921) connections. As a result, the processing load to manage the connections increases in proportion to the increase of the number of devices.
Even if one device can communicate to other devices to which the light does not directly reach by using the infrared ray repeater, each device must mutually set the connections through the infrared ray repeater. In order for N devices to mutually communicate, N(Nxe2x88x921)/2 connections must be set and managed. Therefore, the processing load to manage the connection increases in proportion to the increase of the number of devices.
It is an object of the present invention to provide a data communication apparatus and a method to mutually communicate for a plurality of devices even if the communicatable areas of the plurality of devices do not overlap.
According to the present invention, there is provided a data communication apparatus including a sending means and a receiving means for communicating a radio signal light as a carrier wave for a plurality of other devices each being the data communication apparatus, comprising: discrimination data generation means for generating discrimination data of own device through said sending means; direct communicatable device memory for, when said receiving means receives the discrimination data sent by the other device, storing the discrimination data of the other device as a direct communicatable device for the own device; direct communicatable device list generation means for generating a direct communicatable device list including the discrimination data stored in said direct communicatable device memory, and for sending the direct communicatable device list with the discrimination data of the own device through said sending means; indirect communicatable device memory for, when said receiving means receives the direct communicatable device list sent by the other device, storing the direct communicatable device list as an indirect communicatable device for the own device in relation to the discrimination data of the other device; user data processing means for selecting the discrimination data as a destination address from the discrimination data stored in said direct communicatable device memory and said indirect communicatable device memory, and for sending data with the destination address through said sending means; and relay means for, when said receiving means receives the data sent by the other device, deciding whether the destination address of the received data coincides with the discrimination data of the own device or the discrimination data stored in said direct communicatable device memory, and for relaying the received data to the direct communicatable device of the destination address through said sending means if the destination address coincides with the discrimination data of the direct communicatable device.
Further in accordance with the present invention, there is also provided a method for communicating data among a plurality of devices, each device includes a sending means and a receiving means for communicating a radio signal light as a carrier wave for other devices, comprising the steps of: sending discrimination data of own device; receiving the discrimination data from the other device; storing the discrimination data of the other device as a direct communicatable device for the own device; generating a direct communicatable device list including the destination stored at the storing step; sending the direct communicatable device list with the discrimination data of the own device; receiving the direct communicatable device list from the other device; storing the direct communicatable device list as an indirect communicatable device for the own device in relation to the discrimination data of the other device; selecting the discrimination data as a destination address from the destination data of the direct communicatable device and the indirect communicatable device; sending data with the destination address; receiving the data from the other device; deciding whether the destination address of the received data coincides with the discrimination data of the own device or the discrimination data of the direct communicatable device; and relaying the received data to the direct communicatable device of the destination address if the destination address coincides with the discrimination data of the direct communicatable device.
Further In accordance with the present invention, there is also provided a computer readable memory containing computer readable instructions in each of a plurality of devices to communicate data, each device includes a sending means and a receiving means for communicating a radio signal light as a carrier wave for other devices, comprising: instruction means for causing a computer to send discrimination data of own device; instruction means for causing a computer to receive the discrimination data from the other device; instruction means for causing a computer to store the discrimination data of the other device as a direct communicatable device for the own device; instruction means for causing a computer to generate a direct communicatable device list including the destination stored; instruction means for causing a computer to send the direct communicatable device list with the discrimination data of the own device; instruction means for causing a computer to receive the direct communicatable device list from the other device; instruction means for causing a computer to store the direct communicatable device list as an indirect communicatable device for the own device in relation to the discrimination data of the other device; instruction means for causing a computer to select the discrimination data as a destination address from the destination data of the direct communicatable device and the indirect communicatable device; instruction means for causing a computer to send data with the destination address; instruction means for causing a computer to receive the data from the other device; instruction means for causing a computer to decide whether the destination address of the received data coincides with the discrimination data of the own device or the discrimination data of the direct communicatable device; and instruction means for causing a computer to relay the received data to the direct communicatable device of the destination address if the destination address coincides with the discrimination data of the direct communicatable device.